Verb: Urgent need to have a bowel movement that is so pressing as to require one to utilize a public, and typically disgusting, restroom wihtout enough time to hold it long enough to make it home to a sanitary commode/toliet.

ORIGIN: Term from submarines where by air/balast is quickly released causing the submarine to rise rapidly- see the film Hunt for Red October

Jones had eaten mass quanites of mexican food the night before and was forced to excute an "emergency blow" at the nearest Gas Station.